A wide range of medical procedures involve placing objects, such as sensors, tubes, catheters, dispensing devices, and implants, within the body. Real-time imaging methods are often used to assist doctors in visualizing the object and its surroundings during these procedures. In most situations, however, real-time three-dimensional imaging is not possible or desirable. Instead, systems for obtaining real-time spatial coordinates of the internal object are often utilized.
U.S. Patent Application 2007/0016007, to Govari et al., whose disclosure is incorporated herein by reference, describes a hybrid magnetic-based and impedance-based position sensing system. The system includes a probe adapted to be introduced into a body cavity of a subject.
U.S. Pat. No. 6,574,498, to Gilboa, whose disclosure is incorporated herein by reference, describes a system for determining the position of a work piece within a cavity of an opaque body. The system claims to use a transducer that interacts with a primary field, and several transducers that interact with a secondary field.
U.S. Pat. No. 5,899,860, to Pfeiffer, et al., whose disclosure is incorporated herein by reference, describes a system for determining the position of a catheter inside the body of a patient. A correction function is determined from the difference between calibration positions derived from received location signals and known, true calibration positions, whereupon catheter positions, derived from received position signals, are corrected in subsequent measurement stages according to the correction function.
U.S. Pat. No. 5,983,126, to Wittkampf, whose disclosure is incorporated herein by reference, describes a system in which catheter position is detected using electrical impedance methods.
U.S. Patent Application Publications 2006/0173251, to Govari et al., and 2007/0038078, to Osadchy, whose disclosures are incorporated herein by reference, describe methods for sensing the position of a probe by passing electrical currents through the body between an electrode on the probe and a plurality of locations on a surface of the body. These methods likewise use the electrical impedance of the body in sensing probe position.
The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.